PowerVM

  • 1.  Software iSCSI initiator with Linux taregt

    Posted Thu February 11, 2021 07:50 AM
    Hi,

    I just started trying the new software iSCSI initiator on a 3.1.1.25 VIOS and noticed it wont recognize iSCSI LUNs exported via LIO on to Linux boxes (the Red Hat Ceph 4.2 iSCSI gateway) as MPIO capable devices.
    Has anyone ever tried a similar setup? I think I will need a ODM package, but which one?

    Best Regards,
    Jonas

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    Jonas Jansen
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  • 2.  RE: Software iSCSI initiator with Linux taregt

    Posted Thu February 11, 2021 08:11 PM
    Edited by Sridhar Murthy Thu February 11, 2021 08:43 PM
    Hi Jonas:

    My understanding is VIOS 3.1 allows iSCSI disks to be exported to client logical partitions as virtual disks (vSCSI disks). 

    If I am not mistaken, POWER8 systems have  firmware level requirements while POWER9 may not have any restriction.  Have you checked the firmware level of the system?

    For AIX based LPAR  I used devices.iscsi_sw.rte and it had worked.  I don't know if there is a RPM package released for Linux

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    Sridhar Murthy
    Senior Certified IT Specialist
    IBM
    3039240413
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  • 3.  RE: Software iSCSI initiator with Linux taregt

    Posted Tue February 16, 2021 10:52 AM
    Hi,

    thanks for your replay. We have not figured it out yet, but I am afraid it might be sorting about the way LIO exports the LUNs. According to my googeling the AIX MPIO dowse not relay on alua, but that's the Linux way to do multipath.

    Best regards,
    Jonas

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    Jonas Jansen
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  • 4.  RE: Software iSCSI initiator with Linux taregt

    Posted Fri February 26, 2021 04:21 PM
    Hi Jonas

    AIX, and by extension VIOS, only recognizes a LUN as an MPIO device if there is suitable ODM that matches the device.  AIX queries the vendor ID and product ID in the standard inquiry data and attempts to match that to ODM entries.  If no such match is found, AIX/VIOS creates non-MPIO hdisks with one hdisk per path.

    For regular hardware storage devices, it is the vendor who makes the hardware (whether that be IBM or some other company) who is responsible for doing qualification testing of the hardware with AIX or VIOS.  Once that qualification is complete, the vendor can ship an ODM package that allows AIX to recognize the disks as MPIO disks.

    As you might guess, with something like a Linux software iSCSI target, there really is not a single vendor who could be responsible for such qualification and make support claims.  And so far, the IBM AIX/VIOS development teams have also not taken up that task.  So, I am not aware of any ODM for recognizing Linux iSCSI target disks, and that is a pretty good indication that no one has completed qualification testing in such an environment.

    Finally, just for the record, the AIX/VIOS SCSI drivers most certainly recognize and implement ALUA.  The IBM SVC/Storwize family of storage devices use it heavily, among others.

    Regards,
    Gary Domrow

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    Gary Domrow
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